Peptide hormone
/PEP-tide HOR-mone/
Also known as: protein hormone, polypeptide hormone, endocrine peptide
Definition
A peptide hormone is a hormone composed of amino acids linked together by peptide bonds. Peptide hormones include short peptides (2-3 amino acids), larger peptides (10-40+ amino acids), and proteins. These hormones are synthesized in endocrine cells and released into circulation to act on distant target tissues. Unlike steroid hormones, which can cross cell membranes, peptide hormones are too large and hydrophilic to penetrate cell membranes directly; instead, they bind to cell-surface receptors (typically G-protein-coupled receptors or receptor tyrosine kinases) and trigger intracellular signaling cascades. Examples of peptide hormones include insulin, glucagon, GLP-1, growth hormone, and gonadotropins. In research contexts, peptide hormones are studied to understand their receptor biology, their signaling mechanisms, and their potential therapeutic applications. Many pharmaceutical peptides are engineered versions of natural peptide hormones designed to have improved stability, selectivity, or duration of action.
Peptide hormones are synthesized as larger precursor molecules called prohormones, which are then processed by proteolytic cleavage to generate the mature, bioactive hormone. This processing can generate multiple active peptides from a single precursor; for example, pro-glucagon is cleaved to produce glucagon and GLP-1, two distinct and important metabolic hormones. The processing, transport, and secretion of peptide hormones are tightly regulated, allowing for precise control of hormone levels in response to physiological demands.
The actions of peptide hormones are mediated through their receptors and intracellular signaling pathways. Different tissues express different complements of peptide hormone receptors, allowing the same peptide hormone to produce tissue-specific effects. Dysregulation of peptide hormone systems contributes to many diseases, including diabetes, obesity, and growth disorders. Understanding peptide hormone mechanisms has led to the development of many important therapeutic peptides.